The present patent application relates to internal combustion engines and more particularly to the combustion system of internal combustion engines presenting a new manner of organizing and performing the combustion.
Usually diesel engines have low fuel comsumption and low emissions, but have disadvantages of smoke and roughness which are two main problems on which researchers have been focused. Gasoline engines have high fuel consumption and high emissions. But gasoline engines run smoothly, are easy to cold start and usually have no smoke. The differences come from the different properties of diesel fuel and gasoline fuel, from the different combustion methods and design factors of diesel engines and gasoline engines.
Diesel fuel is easily-self-ignited, not-easily-vaporized, and self-lubricating. As a response to not-easily-vaporized and self-lubricating properties of diesel fuel, diesel engines inject diesel fuel into the high temperature and high pressure air charge in the cylinder near the end of the compression stroke. Injected diesel fuel undergoes physical and chemical changes and ignites itself. And then the combustion of diesel fuel carries out mainly in the manner of diffusing-combustion. Just according to the self-lubricating property of diesel fuel, diesel engines can use high pressure injection to inject diesel fuel near the end of the compression stroke to get good mixing of diesel fuel and air. In order to ignite diesel fuel by high temperature and high pressure, diesel engines use high compression ratio. Diesel engines use diffusing-combustion, therein diesel engines employ fuel-adjust-load and have a large air/fuel ratio. High compression ratio, large air/fuel ratio and fuel-adjust-load make diesel engines have low fuel consumption and low emissions. But diffusing-combustion leads easily to smoke. Diesel engines have poor mixing of diesel fuel and air compared to gasoline engines. Generally speaking, reducing smoke is contrary to reducing running rough. To solve these two problems simultaneously is difficult to do. In fact, today's diesel engines are too rough and too smoky compared with gasoline engines.
The properties of gasoline are it is volatile, not-easily-self-ignited, and not-self-lubricating. Using the property of volatility, conventional gasoline engines supply gasoline fuel into the intake air charge in the intake manifold and use a spark plug instead of high temperature and pressure to ignite the mixture. Also because of the not-self-lubricating property, gasoline engines rarely use high pressure injection in concern about manufacturing and running cost. Gasoline engines have to use low compression ratio and rich mixture compared with diesel engines under the limits of the mixture of gasoline fuel and air. Low compression ratio and rich mixture lead to high fuel consumption and high emissions. Using a throttle to adjust intake charge in order to keep suitable air/fuel ratio also leads to power loss and high fuel consumption. But conventional gasoline engines use a better mixture than that of diesel engines. The method of flame-spreading combustion in the homogeneous mixture gets the benefits of smoothness and no smoke of gasoline engines.
In response to the properties of diesel fuel and gasoline fuel, considering the advantages and disadvantages of diesel combustion system and gasoline combustion system, to combine the properties of diesel fuel and gasoline fuel to develop new combustion system is a important approach to achieve low fuel consumption and low emissions.